> If anyone reading would care to comment, I would still
> like to know why the original query doesn't work.
>
> UPDATE Table_A SET
> Table_A.A = Table_B.A,
> Table_A.B = Table_B.B
> Table_A.C = Table_B.C FROM Table_A INNER JOIN ON
> Table_A.MASTER_KEY = Table_B.MASTER_KEY;
>

1) Missing comma after Table_B.B
2) I have never seen the syntax on line 4. I may be wrong but I don't
believe it is valid SQL syntax. MS probably isn't the benchmark
company for standards compliance.

Adam